This invention relates to a data carrier in the form of a CD-ROM or rewritable CD usually consisting of a circular CD body with an information-carrying layer applied thereto.
The CD is nowadays a mass product which is used for example as a storage medium in computer technology. It is a storage medium on which data and programs, such as system software or computer games, are normally stored permanently during production of the CD. A currently especially widespread embodiment of the CD is one which is only once writable and therefore designated a CD-ROM. The memory content of such a CD, hereinafter referred to as information, can be read out completely and not changed. In particular, no data can be added and no temporary results stored on the CD. CDs are also available which can be rewritten. However, it is frequently undesirable to write temporary results or other temporary data to the same storage medium in which programs, computer games or the like are already permanently stored. Such data will therefore normally be stored on an attached computer. That means that the CD can only be used with this specific computer if the stored temporary results must be reused for processing. It is of course also possible to store the temporary results on a separate storage medium, such as a minidisk, and henceforth leave them with the CD. The CD and the separate storage medium can then be used in any computer which has two suitable interfaces therefor. If the separate storage medium gets lost, however, one simultaneously loses all temporary results irretrievably.
A similar problem arises in connection with the execute or copy protection of information stored on the CD. For the purpose of execute or copy protection of CDs it is known to produce CDs in such a way that they are readable only with additional hardware. The information on the CD can e.g. be encrypted and the additional hardware can contain the data or algorithms necessary for decryption. The additional hardware usually consists of a smart card with e.g. user-specific data and/or the keys or algorithms making it at all possible to decrypt the information stored on the CD. If the smart card gets lost, however, the information stored on the CD can no longer be used. Such a copy protection method is known from DE-A-44 19 115. Here, the execution of software stored on a secondary storage medium is only allowed after legitimation has been performed by means of a smart card introduced for this purpose into a card reader connected with the computer.
A further disadvantage of storing additional and possibly variable data outside the CD on a separate data carrier is that concurrent processing of the CD information and the data of the separate data carrier requires two accordingly designed interfaces. This requires relatively great technical effort.
EP 0 230 069 B1 discloses a smart card having a rotationally symmetric optical storage beside a microchip. The chip can contain a memory (RAM) and a processor which makes it at all possible to read out coded optical storage data. The purpose of the smart card with the rotationally symmetric optical storage is that a rotating storage medium can be read out faster than the magnetic stripes known up to then could be read out translationally line by line. According to this teaching a storage medium known in smart card technology is thus replaced by a storage medium which is completely novel in the field, a rotationally symmetric optical storage. Communication with the chip disposed beside the optical storage is only possible, however, as long as the smart card is not yet rotating. Simultaneous readout of the optical storage and communication with the chip is not possible.